Anode for electrolytic coating



Nov. 9, 1948. A. B. WILSON 2,453,481

I ANQDE F OR ELEGTROLYTI COATING Filed March 14, 1944 2 Sheefs-Sheet 1 rig 1.

Q INVENTOR MD V flbl am BWi/son Nov. 9, 1948. A. B. WILSON moms: FOR ELECTROLYTIC COATING 2 Sheets-Sheet 2 Filed March 14, 1944 Abram BMi/son Patented Nov. 9, i948 ANODE FOR ELECTROLYTIC COATING Abram E. Wilson, Hollidays Cove, W. Va., assignor to National Steel Corporation, a corporation of Delaware Application March 14,

1944, Serial No. 526,393 it 2 Claims. (Cl. 204-,-286) This invention relates to the electrolytic coating of metal strip, particularly to the tinning or galvanizing of steel strip, although it may be useful in coating strip other than steel strip with metals other than tin or zinc.

In one form of electrolytic strip-coating apparatus, the strip is passed over a plurality of electrolyte pans having anodes of the coating metal immersed in the electrolyte contained therein. The electrolyte is circulated through the pans and overflows therefrom, thus coming in contact with the bottom surface of the strip. Contact rolls engaging the, strip are connected to one terminal of a, current source and the anodes are connected to the other terminal. The anodes are in the form of bars and are disposed side by side in banks on guides so they may be moved progressively across theline of travel of the strip. The guides are inclined upwardly to maintain a substantially constant spacing between the strip and the upper surfaces of the anode bars as the latter are dissolved. The bars are provided with spacer projections extending laterally therefrom adapted to engage the adjacent bar, thereby maintaining the bars in slight- 1y spaced relation as they travel along the guides to permit free circulation of electrolyte therebetween. One form of such coating apparatus is disclosed and claimed in a copending application, Serial No. 487,758, filed by C. J. Klein and E. W. Rieger, issued as Patent No. 2,399,254.

The anodes used heretofore have their spacer projections located at a distance inwardly from the ends of the bars suchthat the portions of the bars which actually rest on the supporting guides are spaced apart This leaves portions of the surfaces of the guides between adjacent bars exposed for, substantialpperiods between the periodicmovements of the bars along the guides. It has been. observed, in the operation of electrolytic coating lines, that salts crystallize out of the electrolyte and are deposited on the exposed portions of the guides. These salts are quite, hard and, as a result, the electrode bars ride up on the layers of salt deposited on the guides so that the upper surfaces of the bars, instead of lying substantially in a common plane, are spaced different distances from the path of the strip. This causes a non-uni form coating to be applied to the strip since the amount of the anode metal deposited varies with the distance between the anode surface and the strip. The layer of salt deposited on the guides also interferes with the electrical contact between the anodes and the guides through thereof from the electrolyte. In a preferred embodiment, the anode of my invention comprises a. bar of metal having a substantially uniform cross section along the greater portion of the length thereof. The, bar is provided with spacer projections extending laterally therefrom in the regions in which it engages the supporting guides, usually at the ends of the, bars. The anode of my invention may also be conceived of as a bar having a body portion and end portions of greater thickness than themtermediate or body portion forming the laterally extending spacer projections. These projections are adapted to engage the adjacent anode and extend continuously over the portions of the surfaces of the guides on which the anodes move, thereby fully covering the portions of the guide surfaces which would otherwise be left exposed and subject to the deposition of salts by crystallization from the electrolyte.

Another important advantage arising out of the covering of the carbon anode supports inthe manner just described is that the evolution of tain electrolytic solutions are employed and this free chlorine gas causes conversion of tin in the solution to a stannate, thereby causing objectionable sludging conditions. Where the carbon anode supports are covered by the anode bars this condition. is reduced or eliminated.

. A complete understanding of the invention may be gained from the following detailed description and explanation which refer to the accompanying drawings illustrating the preferred embodiment. In the drawings,

Figure 1 is a plan View of an electrolytepan having my anodes installed therein;

Fig. 2 is a partial section to enlarged scale taken along the plane of line 11-11 of Figure 1; Figure Sis a partial section to enlarged scale taken along the planeof line IIIllI of Figure 1; Figure 4 is a plan view of my anode to enlarged scale; i Figure 5 is an end elevation thereof; and Figure 6 is a, transverse section therethrough taken along the plane of line VI-VI of Figure 4.

Referring in detail to the drawings, 'an electrolyte pan II] is one of a series disposed side by side in a horizontal tier over which the strip to be coated, designated S in Figure 2,.is passed in the direction of the arrow for progressive electroplating in a plurality of; stages. The pan N) is fabricated fromplates and has a protective sheathing l l of rubber or the like over its walls and bottom. Electrolyte is supplied to the pan through an inlet l2 in the bottom and overflows the side walls in such volume as to come in contact with the bottom surface of the strip as it passes over the pan. 1 Overflow chambers I3 on opposite sides of 3 the pan have outlet pipes l4 extending downwardly therefrom.

Anodes l5 disposed side by side and arranged in two banks, as shown in Figure 1, are supported on guides 16 and H. The guides It, as shown in Figure 2, are of box section, being fabricated from plates and provided with rubber sheathing. The guide I! is composed of a slab I 8 of metal, preferably the same metal as that of which the anodes 15 are composed, and a slab I9 of hard carbon thereon. As clearly shown in the drawings, the anodes 15 have their opposite ends resting on the guides 16 andthe slab IS. A separator strip 20 of wood or the like is disposed on the guide I! between the anodes of the two banks. The guides l6 and I! are inclined, as shown in Figure 3. The angle of inclination is chosen so that the upper surfaces of the anodes will lie substantially in a common plane and thus be equidistant from the strip despite the gradual diminution in the thickness of the anodes as the metal thereof is plated onto the strip. It will be understood that the anode l5 shown at the left in Figure 3 represents substantially the size and sectional shape of the anodes as originally deposited on the guides. The anodes are advanced periodically, step by step, so that as their upper surface is dissolved by electrolytic action, it is maintained at substantially the same spacing below the strip. When the anodes have been moved entirely across the electrolyte pan and been reduced to a minimum thickness, they are removed for remelting. The metal slab 18 of the guide I! has a projection 2| extending upwardly at one end thereof, having a terminal Zia therein for attachment to suitable conductors leading to one pole of the current source.

The anode 15, as shown in Figures 4 through 6, has a polygonal section which is substantially uniform throughout the greater portion of its length. The anode is a bar of the metal to be plated onto the strip, such as tin, zinc or the like, and may be conveniently produced by casting in a suitable mold. Adjacent its ends, the bar has a thickness greater than in the intermediate portion forming laterally extending projections 22 adapted to engage an adjacent anode when a plurality of them are disposed in banks, as shown in Figure 1. The bottom face at each end of the anode is bounded by two edges 22' and 22" extending parallel to the longitudinal axis of the bar and constituting the extreme lateral projections on the sides of the bar. The projections 22 serve to space adjacent anodes apart for the greater portion of their length. The projections extend continuously across the portions of the surfaces of the guides engaged by the anodes and fully overlie the parts of such surfaces which would otherwise be left exposed to the electrolyte. That is to say, the bars together with the spacer projections thereof cover the entire portion of the guides with which the anodes are actually in contact. The accumulation of salt deposits on the guide surfaces between adjacent anode bars, as experienced heretofore, is thus effectively prevented. As a result, the ends of the anodes are bottomed flush on the guides. Their upper surfaces lie substantially in a common plane and are thus maintained at the same distance below the path of the strip so that a uniform coating will be plated onto the under surface thereof. Good electrical contact is also maintained continuously between the anodes and the carbon slab l9 It will be apparent from the foregoing that the invention provides an anode for plating baths of the type described which hassa marked advantage over the anodes previously used in such baths. The improved anode has a simple outline so that it may be produced as easily and cheaply as the anodes previously employed and may be as readily handled in depositing it in and removing it from the bath. The same uniformity and speed of coating maybe obtained with my anode as with that employed heretofore.

While I have shown the spacer projections at both ends of the anode bar on the same side thereof, it will be understood that this is not essential since the projection at one end may be on the one side and the projection at'the other end on the other side. This and other like modifications do not alter the principle of the invention and are accordingly intended to be included within the scope of the following claims.

I claim:

1. In an electroplating apparatus wherein a plurality of anodes are disposed in spaced, side by-side relation in a bank in an electroplating bath, the combination of a plurality of anode bars and spaced guides in said bath for supporting the anode bars and over which they may be moved, one of said guides being an electrical contact member for supplying current to the anode bars, each anode bar comprising an elongated body portion, the cross section of which is quadrilateral, and quadrilateral end portions adapted to ride on said guides, said end portions being of greater cross-sectional area than and extending laterall y beyond said body portion, and having coplanar faces parallel to the axis of the body portion, the faces of the end portions resting on the guides, together with the corresponding faces of adjacent anode bars, substantially completely covering the portions of the guides traversed by the anode bars as they are moved therealong,

2. Electroplating apparatus submerged in an electroplating bath comprising anode bars disposed in spaced, side-by-side relation with flat top surfaces lying in a common plane and spaced f guides having surfaces on which the ends of the bars rest and are adapted to slide, one of said guides being an electrical contact member for supplying current to the anode bars, each anode bar having a flat bottom face at each end thereof, the bottom face at each end being bounded by two edges extending parallel to the longitudinal axis of the bar, said edges constituting the extreme lateral projections on the sides of the bar, whereby the bottom faces at the ends of adjacent barsare adapted to lie side-by-side and to form a substantially continuous cover over the surface of the guide on which they rest, the edges on one side of each end of the bar projecting laterally beyond the intermediate portion of the bar, thereby providing a space between adjacent bars.

ABRAM. B. WILSON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Rieger et a1v Apr. 30, 1946 

